Hi Tom, your topic is fascinating, but super wide. Actually reminds me of my own concept..
I am still wondering though what kind of human interaction are you most interested in investigating..
-interaction on the subway (like the video Linda showed us)
- courtship (senior seminar flashback) -parents with their children
- friends -strangers in the street?
what age groups? where do these people live?
the culture these people come from will have a vast impact on the way they interact.. or maybe you are interested in investigating the interactions of people who come together from different cultures..
Again, this topic could be thrilling. But i think you have to narrow it down. in fact, me telling you this makes me think i need to go narrow my topic down..
hope this helped!